Not compiling against glslang

[oneforall2]

FAILED: src/libplacebo.so.264.p/glsl_glslang.cc.o.
ccache c++ -Isrc/libplacebo.so.264.p -Isrc -I../src -Isrc/include -I../src/include -Isrc/opengl/include.
-I../src/opengl/include -Isrc/vulkan -Isrc/opengl/include/glad -I/usr/include/glslang -fvisibility=hidden.
-fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -std=c++11 -O3 -O2 -m64 -fPIC.
-fPIC -pthread -MD -MQ src/libplacebo.so.264.p/glsl_glslang.cc.o -MF src/libplacebo.so.264.p/glsl_glslang.cc
.o.d -o src/libplacebo.so.264.p/glsl_glslang.cc.o -c ../src/glsl/glslang.cc
In file included from /usr/include/glslang/Include/Types.h:47,
from /usr/include/glslang/Include/intermediate.h:57,
from /usr/include/glslang/MachineIndependent/localintermediate.h:42,
from /usr/include/glslang/SPIRV/SpvTools.h:50,
from /usr/include/glslang/SPIRV/GlslangToSpv.h:42,
from ../src/glsl/glslang.cc:28:
/usr/include/glslang/Include/SpirvIntrinsics.h:120:10: error: ‘variant’ in namespace ‘std’ does not name a.
template type
120 | std::variant<const TIntermConstantUnion*, const TType*> value;

[oneforall2]

hmm I added CXXFLAGS=-std="c++17" and it compiles..